thinkharderdev opened a new pull request #1622:
URL: https://github.com/apache/arrow-datafusion/pull/1622
# Which issue does this PR close?
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Closes #132
# Rationale for this change
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Currently, it is assumed that all parquet files in a listing scan will have
the same schema. This will allow support for schema evolution in the underlying
storage layer by merging parquet schemas on read.
# What changes are included in this PR?
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There are three parts:
1. Modify `ParquetFormat` to merge schemas for all listed parquet files
using the underlying `Schema::try_merge` method in `arrow-rs`
2. When reading individual parquet files, map projected column indexes from
the merged schema to the file schema.
3. "Backfill" any missing columns from the merged schema with null-valued
columns.
# Are there any user-facing changes?
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updated before approving the PR.
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Scans that contain heterogenous schemas will attempt to merge the schemas.
If that error was expected then the observed behavior will be different.
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No
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